The life cycle cost of a compressor, or total cost of ownership, adds up everything it will cost between purchase and replacement: purchase and installation, energy, maintenance and downtime. On a machine that runs a lot, electricity is the largest item. To check this in your own case, you need three figures: your running hours, your price per kWh and your quotes.
Our guide what a compressor really costs explains how to estimate the electricity bill and reduce it. This one gives the method to put all the items together and compare two offers.
The four blocks of life cycle cost
| Block | What it covers | When you pay it |
|---|---|---|
| Purchase and installation | Compressor, receiver, dryer, filters, drains, connection, pipework, room ventilation | Once, at the start |
| Energy | Compressor electricity on load and unloaded, dryer electricity | Every running hour |
| Maintenance | Services, filter kits, oil, separator, drains, receiver inspection | According to the hour meter |
| Downtime and contingencies | Lost production, emergency rental, unplanned parts | Rarely, but expensive |
A fifth block is sometimes added, end of life: trade-in or recycling of the machine.
Step 1: set the horizon and the hours
The whole calculation depends on running hours. Choose an analysis horizon, ten years for example, then estimate the hours per year. Two assumptions to adapt:
- One shift, 8 hours a day, 220 days a year: about 1,760 hours a year.
- Two shifts: about 3,500 hours a year.
Over ten years on two shifts, that makes about 35,000 hours. On an existing machine, the controller's hour meter gives the real figure.
Step 2: energy, in kWh first
Calculate energy in kWh, then multiply by your price per kWh. For a fixed-speed machine:
kWh = power × (loaded hours + unloaded share × unloaded hours)
Unloaded, a common order of magnitude is a quarter of rated power. Example for an 11 kW compressor, 35,000 hours, on load 70% of the time:
- Loaded hours: 35,000 × 0.7 = 24,500 h.
- Unloaded hours: 35,000 − 24,500 = 10,500 h, counted at a quarter, the equivalent of 2,625 h.
- Energy: 11 × (24,500 + 2,625) ≈ 298,000 kWh over ten years.
Add the dryer's consumption, stated on its data sheet. With a variable speed machine, unloaded time is reduced: the compressor electricity cost calculator takes this into account.
Step 3: maintenance, as a number of services
On our screw compressors, the first service is at 500 hours, then every 1,500 hours, according to the data sheets. The number of services over the horizon is:
services ≈ 1 + (total hours − 500) ÷ 1,500
For 35,000 hours: 1 + 34,500 ÷ 1,500 = 24 services. Each one uses a service kit matched to the model: multiply by the price on your quote, and add labour if a technician does the work. The screw compressor maintenance guide details what each service includes.
Step 4: the share of energy
Add up the four blocks, in money this time, then calculate:
energy share = energy cost ÷ life cycle cost
A second calculation often speaks louder: the number of hours after which electricity has cost as much as the machine.
break-even hours = purchase price ÷ (power × price per kWh)
With your quote and your electricity contract, you will see that a machine used on two shifts passes this mark quickly. That is why an efficiency gap of a few percent weighs more than a gap in purchase price.
Comparing two offers
To compare two compressors, put them on the same footing:
- Same flow, at the same pressure. Relate energy to the volume of air produced, in kWh per m³: the method is in what 1 m³ of compressed air costs.
- Same scope. A 4-in-1 such as the K 110 integrates receiver, refrigerated dryer and filtration; a standalone compressor such as the S 110 needs these parts and their connection added. Compare the complete installation, not just the machine.
- Same use. A piston compressor such as the E 110, 1.6 m³/min according to its data sheet, is built for intermittent use. At similar flow, the choice between piston and screw comes down first to running hours.
- Same support. AIRSTAHL gives a 2-year warranty and keeps spare parts available for 15 years: check what the other offer provides, because a part you cannot find turns a breakdown into a replacement.
What makes life cycle cost drift
- Leaks, which keep the machine running for nothing, nights included.
- Pressure set too high: roughly 7% more energy per extra bar, as a common order of magnitude.
- A badly sized machine, too large and often unloaded, or too small and always flat out.
- Postponed maintenance: clogged filters and a saturated separator push consumption up.
A compressed air audit measures your real consumption and shows where to act. For a new project, the configurator sizes the machine from your tools, and a quote request gives you the purchase and maintenance figures to put into the calculation.